This invention relates to a detector arrangement for electromagnetic radiation comprising at least an absorbing element and a sensor arranged in operational connection with each other and at least the sensor being arranged to be bendable in response to electromagnetic radiation.
This invention relates further to a method for measuring electromagnetic radiation. In the method an absorbing element and a sensor are arranged in operational connection with each other. Electromagnetic radiation is directed on to the absorbing element whereby a bending of the sensor is caused. Bending of the sensor is measured.
A detector for electromagnetic radiation is a detector that reacts to electromagnetic radiation.
Prior art comprises several types of detectors for electromagnetic radiation: Thermocouples and thermopiles use the thermoelectric effect. Typically, they have a large thermal mass, long response times and rather limited sensitivity.
Bolometers are based on changes in resistance. Conventional bolometer structures have large thermal mass. By using micro-machined, suspended foils mass can be reduced and rise time shortened.
Solid-state detectors for electromagnetic radiation, such as quantum well devices, are based on semiconductor phenomena. As a consequence of their high inherent thermal noise, these devices must generally operate at a reduced temperature. Their spectral response is also severely limited by the intrinsic properties of the semiconductor materials.
The currently fastest and still quite sensitive bolometers are based on superconductors, which are voltage or current-biased into the transient-edge of the superconductive material. These devices, however, are workable only in cryogenic temperatures well below 1 K.
Golay cells follow thermal expansion. Gas inside a chamber expands upon heating and causes a Mylar-film to deform. Golay cells are sensitive, but very delicate.
Patent publication EP 0 893 675 B1 discloses a luminous intensity sensor element having a flat disk-shaped element made of material with a high thermal expansion coefficient and of low thermal conductivity and on opposite faces, an optically absorbent layer and a reflecting layer. On receiving excitation radiation, the optically absorbent layer is heated and transmits heat to the disk-shaped element, which is heated internally in spatially non-uniform manner and is deformed together with the superimposed reflecting layer. The reflecting layer receives an incident reference light beam to generate a reflected light beam having optical characteristics depending on the aforementioned deformation and varying in response to the excitation radiation. The structure of the sensor element is fairly complicated with three different layers. The sensor element is a membrane and therefore it is fastened by all of its edges which restricts its movements and weakens linearity.